This invention relates in general to manipulating devices and in particular to a new and useful device connected between a working arm and a tool in which a stress of two of the operating parts is effective to disconnect the drive.
Similar safety devices are disclosed in German Pat. No. 27 17 871 and in German AS No. 27 49 603.
The problem posed is to abruptly stop the automatically controlled motion of a manipulator as soon as one of the constructional parts of the manipulator unexpectedly encounters an obstacle. It is mostly the tool of the manipulator which undesirably strikes against a portion of the workpiece to be handled. By stopping the automatically controlled motion, damages are to be avoided.
In prior art designs, such safety devices are preferably provided at the end of the cantilever arm of the manipulator, between the last member and the tool. In the design of the two above references, the constructional parts connected to each other are associated with each other through a non-positively engaged guidance. The force holding the parts together and produced by one or more springs is so strong that under normal operating conditions, the connection of the constructional parts joined to each other is relatively immovable. However, as soon as the tool or another part of the manipulator unexpectedly encounters a resistance, the non-positive connection of the constructional parts yields, the yielding motion is detected by a switch responsive thereto and used for disconnecting the drive.
The prior art safety devices are designed to react to three-dimensional changes in their non-positively maintained centered position. This is easily obtained in instances where the two constructional parts move toward each other coaxially or are turned relative to each other in the circumferential direction. Collisions observed in practice, however, occur under forces which do not act in specific directions, to which the prior art devices are not so well responsive as to loads in the axial direction or transversely thereto.